Ballistics experts concluded the gun used by Evan Ebel in Texas was the same weapon used in the shooting death of Tom Clements

This undated photo released by the Colorado Department of Corrections shows paroled inmate Evan Spencer Ebel. Ebel, 28, is the man who led Texas authorities on a 100 mph car chase that ended in a shootout Thursday, March 21, 2013, and may be linked to the slaying of Colorado's state prison chief. (AP Photo/Colorado Department of Corrections)

The El Paso County sheriff's office said that "unique and often microscopic markings" found on shell casings in Texas and Colorado leads investigators to conclude that the gun Evan Ebel used to shoot at authorities in Texas was the same gun used to kill Tom Clements at his home on Tuesday.

It had been known that the casings found at both scenes were of the same caliber and brand but Monday's announcement was the first time Colorado investigators made a direct link between Ebel and Clements' death.

What remained unknown though was why Clements was killed when he answered his front door Tuesday night and whether Ebel acted alone.

"There are no answers at this time surrounding motive and gaining these answers could be a lengthy process for investigators," sheriff's spokesman Lt. Jeff Kramer said in statement.

The announcement came just hours after hundreds of people, including corrections officials and guards from as far away as Morocco, gathered for a memorial service to honor Clements.

The crowd at New Life Church included 39 current and former corrections' chiefs as well as guards from 14 states. A delegation of corrections officials from Morocco also attended along with dignitaries including Gov. John Hickenlooper and U.S. Attorney John Walsh.

Hickenlooper and his widow both spoke about Clements' strong belief in redemption. His family said he decided as a teenage to work in corrections after visiting his uncle in prison, and he worked to reduce the use of solitary confinement in Colorado prisons.

Standing with her two daughters, Lisa Clements said her husband of 28 years would want justice as well as forgiveness.

"We want everyone who hears Tom's story to know that he lived his life believing in redemption, in the ability of the human heart to be changed. He would want justice certainly but moreover he'd want forgiveness. Our family prays for the family of the man who took Tom's life and we will pray for forgiveness in our own hearts and our own peace," said Lisa Clements, a psychologist who oversees Colorado's state mental health institutes.

Hickenlooper, who hired Clements about two years ago, told mourners that Clements was both pragmatic and principled.

"He had common sense and he had courage," Hickenlooper said.

Authorities say the car Ebel had in Texas is also similar to one seen not far from Clements' home the night he was killed.

A federal law enforcement official said Ebel had been a member of the 211s, a white supremacist prison gang in Colorado. El Paso County sheriff's spokesman Lt. Jeff Kramer said Monday that investigators are trying to determine whether there was any gang involvement in the killing, but he stressed that's only one aspect of a broad investigation.

Denver police say Ebel is also a suspect in the March 17 slaying of pizza delivery man Nathan Leon.

Hickenlooper is a longtime friend of the suspect's father, attorney Jack Ebel, who testified two years ago before state lawmakers that solitary confinement was destroying his son's psyche.

Hickenlooper confirmed he mentioned the case to Clements as an example of why the prison system needed reform before the job was offered, but the governor said he did not mention Evan Ebel by name.

There was no indication that Hickenlooper's relationship with Jack Ebel played a role in the shooting. Hickenlooper said he did not having any role in Evan Ebel's parole in January.

Jack Ebel issued a statement offering condolences to all those who have suffered from his son's actions.

Clements, born in St. Louis, worked for 31 years in the Missouri Department of Corrections, both in prison and as a parole officer, before taking the top corrections' job in Colorado just over two years ago. He began a review of the state's solitary confinement system and eventually reduced the number of prisoners being held in solitary. He closed a new prison built specifically to hold such prisoners — Colorado State Penitentiary II.

His work won praise from groups including the American Civil Liberties Union and the union representing prison workers, which called him a "leader who looked out for those he led."

Officials took additional security measures after Clements' death and placed the state prisons on lockdown Friday.

Following Clements' killing, corrections professionals said their jobs have grown more dangerous for themselves and their families because of the growing influence of prison gangs, their ability to communicate with affiliates on the outside through smuggled cellphones and the ease with which people can be found and tracked online.

Clements is at least the second head of a state prison system to be killed. The top administrator of the Oregon Department of Corrections, Michael Francke, was stabbed to death outside his office in 1989 in what prosecutors described as a bungled car burglary. A former state prison inmate was found guilty of aggravated murder in 1991 and sentenced to life in prison.